Yes keep him on. If he were to fall ill before the divorce is finalized without health insurance the debt from medical treatment could be a marital debt. Rather than cancel insurance I would suggest that you contact your attorney to file a motion for temporary support and ask the Court to order him to pay certain expenses for you and/or his portion of the health insurance.

This comment is being left for informational purposes only and based solely on the information provided in the question. This comment does NOT create an attorney - client relationship. An attorney should be contact directly and given the full details of the specific circumstances in order to be best able to assist in the issues at hand.

As stated, it is most likely in your best interest to keep them on your health insurance. Downstate, judges get extremely upset when you unilaterally remove someone from health insurance.
Although it is expensive, it is not nearly as expensive as being responsible for big medical bills. You should talk to your lawyer about this.
If you don't have a lawyer – get one.

If you found this Answer to be helpful, please mark it as such. Remember, however, free advice is worth every penny you paid for it. This is only generalized commentary on your question. It is not to be taken as legal advice. I am a lawyer – but not your lawyer! Even "in person" interviews leave attorneys with plenty of questions – the Internet makes it crazy!
Thank you
Chuck Watson
217.544.6165